Concomitant polymorphs of methoxyflavone (5-methyl-7-methoxyflavone)

• Published in: RSC advances 2016-01, Vol.6 (45), p.3879-38715
• Main Authors: Gong, Ningbo, Hu, Kun, Jin, Guimin, Du, Guanhua, Lu, Yang
• Format: Article
• Language: English
• Subjects: Absorption; Asymmetry; Crystallization; Differential scanning calorimetry; Diffraction; Fourier transforms; Infrared spectroscopy; X-rays
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c6ra05995c

A novel metastable polymorph and an unstable amorphous phase of methoxyflavone were discovered after a decade since the first report of the X-ray crystal structure of this bioactive compound. The new polymorph (form B) was crystallized from a single solvent that produced two different polymorphs concomitantly, which is different from the reported structure of form A (CCDC code: FATYOP). The two polymorphs crystallized in the same P 2 1 / c space group, the asymmetric units in form A contain one and form B contains two molecules with different conformations. The conformational differences and the weak CHO intermolecular interactions played a major role in generating the methoxyflavone polymorphs. The polymorphs were characterized by X-ray diffraction, differential scanning calorimetry and FT-IR spectroscopy. Thermodynamic properties were unambiguously established using room-temperature competitive slurry experiments, solid-state milling and heating. Form A was more stable than form B, the amorphous phase was unstable and easily converted to form A at room temperature in 30 minutes. Form A had higher absorption area, the C max and AUC of form A were approximately two times those of form B. A novel metastable polymorph and an unstable amorphous phase of methoxyflavone were discovered after a decade since the first report of the X-ray crystal structure of this bioactive compound.